But battery-electric cars are perceived to have drawbacks--including recharging time--and it's unclear whether the largest, heaviest vehicles can practically be powered by batteries alone.

For a few decades now, most global automakers have had research and development projects to test the practicality of electrically-driven vehicles with only small battery packs.

Instead, their electricity is generated by fuel cells that turn oxygen from the atmosphere and compressed hydrogen into electricity and water vapor. (Technically an emission, but so what?)

The first Hyundai Tucson Fuel Cell crossover utility was leased this spring in southern California.

Both Toyota and Honda are expected to follow suit, offering small numbers of hydrogen fuel cell vehicles for lease in limited regions of the country between now and 2020.

But unlike electricity, which reaches every household and building in some form, hydrogen will require the construction of expensive dedicated fueling sites.

The hydrogen has to be produced by using quite a lot of energy to break down a feedstock (water, natural gas, or other hydrogen-carrying compounds) to get pure hydrogen (H2), which then has to be compressed and transported to the fueling locations.

The general consensus is that using the same amount of electricity with the same carbon footprint to produce hydrogen, or to recharge a battery, gets you more miles in the electric car than in the hydrogen powered car.

Finally, there's the compliance-car issue. In the short term, hydrogen vehicles are being put on the road largely to comply with California's zero-emission vehicle rules, not because there appears to be noticeable market demand for them.

These are all rich issues that deserve greater exploration. From our point of view, what better place to do so than on Green Car Reports?

Yet a small portion of our readers have objected to such articles, seemingly on the grounds that fuel-cell vehicles are a sham, a delaying tactic, and built by makers determined to continue selling gasoline vehicles as long as possible.

All of which may be true.

But we feel such issues are best debated in the open, robustly (but politely and respectfully).

We're not going to suppress coverage of any type of vehicle because (some) readers don't happen to like it.

Perhaps the most comprehensive summary of the issues comes from Joan Ogden, a professor of environmental science and policy in the Institute of Transportation Studies at the University of California--Davis.